The increasing use of immunotherapy has led to a substantial population of people with altered immunologic function. Last year alone, 45,000 hematopoietic stem cell transplants (HSCTs) wereperformed worldwide. Immune recovery following HSCT can take years. This represents a significant population of people vulnerable to infection from a variety of sources. One strategy used to enhance immune reconstitution is adoptive T cell therapy. Data from a recent phase I/II study confirms the importance of reconstitution with antigen experienced T cells for the development of protective immunity after high dose chemotherapy and stem cell rescue for multiple myeloma. As cellular therapy becomes more commonplace, the field of transfusion medicine is perfectly . positioned to take the lead in developing protocols for immunologic repletion. Dr. Aqui has completed residency training in clinical pathology and is currently a Transfusion Medicine fellow at the Universityof Pennsylvania. The proposed 5 year training program is designed to allow Dr. Aqui to develop expertise in cellular therapy and gain experience in the design and implementation of patient-oriented research. Dr. Aqui will pursue her career development under the mentorship of Dr. Carl June. Dr. June is the Director of the Translational Research Program of the Abramson Family Cancer Research Institute (AFCRI), and has pioneered translational research in T cell biology and adoptive immunotherapy of cancer and HIV infection. Dr. Aqui proposes to use the diverse resources of the AFCRI, the Department of Pathology, and the University of Pennsylvania to test the following central hypothesis: infusion of T cells costimulated with anti-CD3/CD28 beads accelerates quantitative and qualitative immune reconstitution. The specific aims of this study are provide a comprehensive assessment of immune recovery kinetics, which include: 1) evaluating immunological recovery after allogeneic HSCT with costimulated allogeneic T cell infusions; 2) determining the contribution of costimulated autologous T cells in vaccine response after HSCT; and 3) identifying barriers to immune recovery in both allogeneic and autologous HSCT. These studies will provide a foundation on which to develop future integrated immunotherapy strategies, including the use of costimulated T cells, targeted at increasing immune responsiveness in the post-transplant period.